As is known, some currently marketed cycling shoe models comprise an appropriately shaped vamp; a rigid sole stitched and/or glued to the bottom of the vamp; an arch support fixed to the sole, inside the vamp; and a number of straps by which to tighten the vamp and immobilize the user's foot inside the shoe.
More specifically, the part of a cycling shoe vamp corresponding to the instep of the foot has a longitudinal opening or slit sized to permit easy insertion of the foot inside the shoe, and the straps are spaced along the vamp, astride the longitudinal opening or slit, so that each brings together and secures locally to each other the two opposite lateral edges of the vamp laterally defining the opening, to tighten the vamp adjustably to the user's foot.
Some cycling shoe models of the above type have “Velcro-fastened” straps comprising a slip ring fixed stably to the vamp, close to one of the two lateral edges of the vamp laterally defining the longitudinal opening of the shoe; and a fastening strip, which is secured at one end to the vamp, close to the other of the two lateral edges of the vamp laterally defining the longitudinal opening of the shoe, and is designed to thread through the slip ring and fold back on itself so that one end of the strip rests on top of the other. The fastening strip also has two Velcro inserts located at the two ends of one of the two faces of the strip, and which are superimposed and adhere to each other when the strip is folded back on itself.
Because the “Velcro” fastening system fails to ensure sufficient long-term stability, some cycling shoe manufacturers have thought to fit the two Velcro inserts centrally with two small toothed plastic plates, which have a serrated profile to mesh with each other when the two Velcro inserts are superimposed, so that pull stress tangent to the plane of the fastening strip, and therefore to the surfaces of the two Velcro inserts, is transmitted directly to the two toothed plates, with no stress on the inserts.
Though successful in preventing slippage of the two ends of the fastening strip caused by pull stress, in use, tangent to the plane of the fastening strip, positioning the two toothed plates centrally on the Velcro inserts in no way counteracts parting of the two inserts caused by intrinsic “slackening” of the material.
As a result, the two toothed plates tend to part gradually until they are suddenly released, thus resulting in immediate slackening of the fastening strip caused by the pull stress tangent to the surfaces of the Velcro inserts.